In a magnetic field detection device which outputs a detection signal corresponding to a magnetic field (external magnetic field) applied from an outside thereof, there is known, as a detecting element, a magneto-resistance element using a magneto-resistance effect of a magnetic material in addition to a Hall element using a Hall effect of a semiconductor. As the magneto-resistance element, there are known an anisotropic magneto-resistance (AMR) element using an anisotropic magneto-resistance effect of metal, a giant magneto-resistance (GMR) element using a giant magneto-resistance effect, a tunnel magneto-resistance (TMR) effect using a tunnel magneto-resistance effect, and the like. An SN ratio of the magnetic field detection device is improved as an output of a magnetic field detection element with respect to the external magnetic field increases, and hence attention is focused on a magnetic field detection device using the GMR element or the TMR element by which a larger output can be obtained.
As a basic structure of the GMR element or the TMR element, there is known, for example, a spin valve structure disclosed in Patent Document 1.
The spin valve structure is a structure in which a first anti-ferromagnetic layer, a first ferromagnetic layer, a first non-magnetic layer, and a second ferromagnetic layer are stacked. In a magneto-resistance element which has the spin valve structure, a magnetization direction of the first ferromagnetic layer is fixed to one direction owing to an exchange-coupling magnetic field with the anti-ferromagnetic layer, and thus the first ferromagnetic layer is referred to as a fixed layer. On the other hand, a direction of a magnetic field of the second ferromagnetic layer is freely rotated owing to the external magnetic field, and thus the second ferromagnetic layer is referred to as a free layer. A resistance of the magneto-resistance element which has the spin valve structure changes in accordance with an angle formed by magnetization vectors of the fixed layer and the free layer. That is, a resistance value of the element changes through a change in magnetization direction of the free layer owing to the external magnetic field, whereby it is possible to detect a direction of the external magnetic field by detecting a change in resistance value of the element.
Here, in the TMR element, an insulating material such as AlOx or MgO is used for the first non-magnetic layer to detect a change in current flowing in a direction perpendicular to a main surface of a layer, and in the GMR element, a conductive material such as copper (Cu) or ruthenium (Ru) is used for the first non-magnetic layer to detect a change in current flowing in a direction parallel to the main surface of the layer.
Magnetization directions of the fixed layer and the free layer are caused to be substantially perpendicular to each other when the external magnetic field is not applied, whereby it is possible to form the TMR element and the GMR element capable of obtaining a linear output with respect to the external magnetic field.
Further, as a conventional magnetic field detection device, there is known, for example, a rotation sensor using a magneto-resistance element as described in Patent Document 2.
Patent Document 1: Japanese Patent Publication No. 08-21166 (1996)
Patent Document 2: Japanese Patent Application Laid-Open No. 2005-331296
In the conventional magnetic field detection device described above, a magnetic body is provided at a position apart from the magneto-resistance element for adjusting a magnetic field applied to the magneto-resistance element. However, the magnetic field applied to the magneto-resistance element greatly depends on an arrangement of the magnetic body, which causes a problem that, even in a case where the arrangement of the magnetic body is slightly deviated from an original position, the magnetic field is greatly affected.
Particularly in a case where the magneto-resistance element is downsized or in a case where the magnetic field detection device itself is downsized, there is a problem that an allowance for arrangement deviation of the magnetic body is reduced, and thus an error in detection value of the magnetic field detection device is increased, leading to a decrease in yield when the magnetic field detection device is manufactured.